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2021-08-14 22:01:26 -0600 received badge  Notable Question (source)
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2017-10-12 09:26:26 -0600 edited question Comm/Proto Hospital Reference Building: Inaccurate energy use due to unrealistic geometry?

Comm/Proto Hospital Reference Building: Inaccurate energy use due to unrealistic geometry? EDIT 10/12/2017 I am going to

2017-10-12 09:17:28 -0600 commented question Comm/Proto Hospital Reference Building: Inaccurate energy use due to unrealistic geometry?

Thank you both for your comments. Larry: Currently I have just been using vanilla EnergyPlus. Almost zero experience wi

2017-10-12 09:17:28 -0600 received badge  Commentator
2017-10-10 10:12:38 -0600 asked a question Comm/Proto Hospital Reference Building: Inaccurate energy use due to unrealistic geometry?

Comm/Proto Hospital Reference Building: Inaccurate energy use due to unrealistic geometry? I have been looking into usin

2017-08-12 16:19:22 -0600 commented answer EnergyPlus Detailed hourly load distribtuion

Feel free to remove this comment if it's not appropriate for the stackexchange-type site format, but I was going down th

2017-08-03 09:13:42 -0600 commented answer Anyone facing problem in simulating Prototype Building Models?

Thank you for the extensive answer. I ran into a similar problem on ASHRAE90.1_Hospital_STD2007_Baltimore.idf Following

2017-07-19 13:34:01 -0600 commented answer What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings?

Matt! Funny running into you here! The answer and references are much appreciated!

2017-07-19 11:32:28 -0600 commented answer What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings?

Thanks for the info, and the reminder about the curves taking into account static pressure reset. This might be as good

2017-07-19 11:29:30 -0600 edited question What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings?

What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings? I know they're not Appe

2017-07-19 09:33:21 -0600 answered a question IDF Editor "Objects" portion of window missing

The issue eventually resolved itself on my work machine. Unfortunately, I did not have a chance at the time to note if a

2016-07-06 07:32:00 -0600 commented question What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings?

The original "reference" buildings, specifically the 2004 "New Construction" buildings.

2016-07-05 20:12:31 -0600 asked a question What is the source for the VAV fan power coefficients in the DOE Commercial Reference Buildings?

I know they're not Appendix G values, and I can't seem to find a mention of where they're sourced from. An internal NREL project?

Any help would be appreciated!

Edit: For reference, here is a Google Sheets plot of fraction of full load fan power versus fan part load ratio for 90.1-2004 Appendix G and the VAV fans in the Commercial Reference Building Large Office ("new", meeting 90.1-2004)

2016-02-15 15:09:51 -0600 asked a question Is the Operational Fault model for Coil Fouling working in v8.4?

Hi,

I've been experimenting with the coil fouling operational fault model in EnergyPlus v8.4, and have been having problems getting any difference in results from it.

Currently, I am trying to get the coil fouling module working with the 5ZoneAirCooled.idf example building that is included with EnergyPlus v8.4. I add the elements, select both of the cooling coils, and have put in what I consider appropriately small UA values (about 1/2 of the nominal UA value listed in the HTML file that is generated).

image description

However, after running my "fouled" file, I get the exact same results as the original. I'd expect, at the least, to have increased pump energy from the reduced waterside dT across the coil.

Running the 5ZoneAirCooled.idf models (original and fouled) in v8.3 results in numbers I would expect. E.g. a slight increase in pump energy.

Reducing the UA values further in both cases results in the same qualitative results: v8.4 shows no difference, v8.3 shows a noticeable difference.

Any help or insight would be appreciated!

2015-09-29 11:35:01 -0600 asked a question Increased cooling and heating energy when using cooling-coil fouling module?

edit: modified to make clear that I'm only modifying cooling coil UA values.

I'm using the DOE Commercial Reference Buildings to perform simulations involving the cooling coil-fouling module introduced in v8.3. For the purposes of this question, I'm going to talk about the Large Office building in Phoenix AZ.

I have modified the rated UA via the coil fouling operational fault modeling to approximately 86% of its "clean" value for cooling coils. This produces some expected effects, e.g. pump energy goes up due to a reduced waterside dT across the coil for an equivalent load. Another "expected" effect is that the amount of cooling energy use goes up. I put "expected" in quotes because I am not aware of what effect fouling has on the chiller models used in EnergyPlus. As a wholly unexpected effect, the gas heating energy goes up. This occurs over the summer months, not the winter months. My question is "Why does this occur?"

A few thoughts thus far:

1) When I convert the cooling energy to cooling load (via COP) and the heating energy to heating load (via boiler efficiency), the amounts just about even out. Is the heating load a result of compensating for over-cooling? Why would over-cooling occur in a situation when UA is reduced?

2) Are the increases in cooling and heating energy unrelated to one another? If that is the case, how does changing the cooling coil UA increase the heating?

3) For the Large Office Commercial Reference Building, the increase in heating seems to be occurring in the warmer (1A through 4A) and drier (2B through 6B) climates, though it is more pronounced in the climates that are both warm and dry (2B and 3B).

Presently, I have been unable to formulate a system operating condition where these results make sense to me. Am more than a bit puzzled, and any help would be appreciated.

2015-09-28 13:37:40 -0600 commented answer IDF Editor "Objects" portion of window missing

@JasonGlazer Thank you for your recommendations, but it seems my problem has persisted.

2015-09-21 12:28:30 -0600 asked a question IDF Editor "Objects" portion of window missing

I feel rather silly posting this, but here it goes. This is less of a usage question and more of a "can't figure out why this bug is occurring" question. The issue is that a portion of the IDF Editor window, where you add and enter Object values, is not there. The top portion of the image shows a correctly working IDF Editor, while the bottom portion shows the IDF Editor on the machine with the issue.

image description

Pertinent information

  • Windows 7 x64 machine, up to date
  • v8.3 of IDF Editor, clean install
  • Occurred originally with all versions of E+ (8.3, 8.2, 7.2) installed on machine
  • Occurs on one machine specifically, works fine on another up to date Windows 7 x64 machine
  • User Access Control windows pops up every time IDF Editor is run
  • Can still add, delete, etc. Objects, just can't see them or click on them

Have tried uninstalling/reinstalling, different window layouts, running in compatibility modes, checking permissions on the EPlus install folder.

Any help or suggestions would be greatly appreciated.

2015-03-31 12:18:39 -0600 commented answer What are recommended heat rates for people?

I'd like to add that I believe the ASHRAE Load Calculations Manual has expanded information on occupants that aren't standard male adults (I saw some of the tables in a Carrier Design Guide, I think). For example, if you're doing load calcs for FCUs or GSHPs for a K-6 school, having more accurate values for tiny humans helps. The President of the firm I worked for out of school scolded some of us younger engineers once for using the adult-male values in such a situation, so I tend to remember it. :)

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2015-03-30 11:44:01 -0600 answered a question Difference in handling heating load and component sizing, EnergyPlus v7.2 vs. v8.2?

I think I have found the issue, and the solution fixes the zero load in 7.2 as well as 8.2 in the Hospital file. In short, the "WinterDesignDay" category in scheduled loads should specify zero percent load from people, equipment, lights, or anything else that could be taken "credit" for during the design heating calculations. Whatever the changes were in the reheat coil sizing from 7.2 to 8.2 seemed to make the problem more visible.

In the case of (at least) the hospital file, there were low, but non-zero, values for a number of the occupancy and equipment schedules under the WinterDesignDay day. These heat gains offset the envelope heating loss, resulting in no heating. Zeroing these heat gains fixed most of the problem. So, the problem is (un)fortunately as simple as the heating design load calculations being performed incorrectly.

A problem with unmet heating hours in one interior zone remained, and I believe this is addressed in this question, as well as this thread in the Yahoo Group. It seems to be a larger issue with reheat coil sizing for interior zones.

2015-03-25 09:25:13 -0600 received badge  Editor (source)
2015-03-25 09:19:53 -0600 commented answer Difference in handling heating load and component sizing, EnergyPlus v7.2 vs. v8.2?

Annie, thank you for the information. I ended up changing the action on the dampers from "normal" to "reverse" in my model. This had the effect of changing the heating load on the zones that already registered having a heating load, but had no change on the zones that showed no heating load.

The lack of heating in these zones also changes the number of hours of setpoint not met during occupied heating from 0 to ~5000, so I can't say I trust the "new" evaluation of the heating load equipment, and am convinced something else must have changed. Will update some of the info above mentioning this.

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2015-03-15 17:41:02 -0600 asked a question Difference in handling heating load and component sizing, EnergyPlus v7.2 vs. v8.2?

2015 03 25 - Added some new information at the bottom

I am currently using the 1.4 versions of the DOE Commercial Reference Buildings (2004 construction) for research purposes. They are provided as EnergyPlus v7.2 IDF files via the web. I recently converted them to v8.2 using the IDF Updater, changing nothing else. There seems to be a difference in how VAV reheat coils are auto-sized and handled. I first noticed this in the Hospital Commercial Reference Building. (Simulation was run in Baltimore climate and, again, 2004 construction).

Both the 7.2 and 8.2 versions of the file generate error messages like this when run:

** Warning ** Calculated design heating load for zone=CORRIDOR_NW_FLR_3 is zero.
** ~~~ ** Check Sizing:Zone and ZoneControl:Thermostat inputs.

However, only the 8.2 version generates the following error message:

** Warning ** The design coil load is zero for Coil:Heating:Water CORRIDOR_NW_FLR_3 VAV BOX REHEAT COIL
** ~~~ ** The autosize value for maximum water flow rate is zero
** ~~~ ** To change this, input a value for UA, change the heating design day, or lower
** ~~~ ** the system heating design supply air temperature

Looking at the html table outputs, the difference manifests in the coil sizing summary. The 7.2 entry:

Maximum Air Flow Rate [m3/s] Maximum Reheat Water Flow Rate [m3/s] Reheat Coil Sizing Air Volume Flow Rate [m3/s]
CORRIDOR_NW_FLR_3 VAV BOX COMPONENT 1.34 0.000367 0.403147

versus an 8.2 entry:

Design Size Maximum Air Flow Rate [m3/s] Design Size Maximum Reheat Water Flow Rate [m3/s] Design Size Reheat Coil Sizing Air Volume Flow Rate [m3/s]
CORRIDOR_NW_FLR_3 VAV BOX COMPONENT 1.34 0.000000 0.403147

As one can see, the difference is in the maximum reheat water flow rate.

More importantly, this manifests itself in the inability of these zones to be heated, which leads to an unrealistically low heating energy use, and unmet heating hours. I've gone through the IDF files in their respective editors, and can't seem to find a difference in the input.

So the primary question is:

1) How do I get v8.2 to treat the file the same as v7.2 and provide a maximum VAV reheat coil flow rate that is not zero, even though the calculated load is zero? (I'd prefer to find a way that isn't manually inputting explicit values, if possible)

With the related questions:

2) How and why does this happen?
3) Would this affect other things that I need to be concerned about?

---- New Information 2015 03 25

The difference also manifests itself in the number of occupied heating hours where setpoint is not met. For example, in the zone mentioned above, the 7.2 run had 0 hours, while the 8.2 run had ~5000. This leads me to not have confidence in the "new" evaluation of the zone's needs.

Some possibly relevant items from the "Known Issues 8.2" document are:

3580 The sizing algorithms for reheat coils in ... (more)

2015-02-05 14:02:00 -0600 received badge  Teacher (source)
2015-02-05 13:57:00 -0600 answered a question Appendix G Pumps Input Power

It's been a few years since I last worked on an Appendix G calculation for LEED, but I don't recall any sort of credit. After skimming through the latest edition of 90.1, it still doesn't appear that there is one. I've got a few other thoughts, forgive me if you're familiar with the concepts already or if I'm talking too simply.

  • Make sure that you're using what you think your system's actual maximum operating condition will be, which may differ from what's scheduled. That is, the older PMs where I worked would throw a lot of slop (a technical term, obviously) on pump head sizing calculations to keep from getting burned down the road. However, in my model's design head I'd consider the pump head calculations without the liability-insurance-safety-factor on it. So, think about what you think the head will be operationally. (Analogous to the difference between load and energy calculations, I'd say) edit: to clarify, talking about a variable speed pump in this situation
  • I'd take full credit for what I knew about "my" system versus the App G system to squeeze what I could out of it...
  • The situations where the App G pump would ride the pump curve rather than have variable speed
  • The VFD curve packaged in the energy simulation software versus the actual curves from the specified manufacturer
  • Make sure the pump minimum turndown on your system isn't too high, check your chiller/tower GPMs vs time to see if they make sense, etc.

I'll admit that a good portion of the work I did was big ground-coupled heat pump systems, so the pumping energy tended to kill us regardless.

Not sure if any of this helps, but good luck!

2015-02-05 13:02:53 -0600 commented question How can I change the unit from kWh to kWh/m2?

@Antop Just for clarification, are you using EnergyPlus?

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